1. Field of the Invention
Embodiments of the present invention relate to a solution of a gallium phthalocyanine, a method for preparing the same, a method for producing a gallium phthalocyanine crystal, a method for purifying a composition containing a gallium phthalocyanine, and a method for producing an electrophotographic photosensitive member.
2. Description of the Related Art
A gallium phthalocyanine represented by the formula (2) (hereinafter, also referred to simply as a “gallium phthalocyanine”) has excellent stability and photosensitivity and thus has been widely used as, in particular, a charge generation material for use in an electrophotographic photosensitive member,
wherein, in the formula (2), X1 represents a chlorine atom or a hydroxy group. X1 is also referred to as a ligand (axial ligand) of the gallium atom of the gallium phthalocyanine.
Japanese Patent Laid-Open No. 6-279698 discloses an acid pasting process in which a gallium phthalocyanine is dissolved in a concentrated sulfuric acid and then treated for the purpose of using the gallium phthalocyanine as a charge generation material for an electrophotographic photosensitive member.
However, concentrated sulfuric acid is a strong acid. Thus, in the case where the gallium phthalocyanine is used as a charge generation material for an electrophotographic photosensitive member, a neutralization step is required. A solution of a gallium phthalocyanine (or a composition containing a gallium phthalocyanine) in the related art is difficult to purify because of its high viscosity and thus severely restricts preparation conditions and storage conditions.
Japanese Patent Laid-Open No. 2010-202747 states N-methylpyrrolidone, dimethyl sulfoxide, dimethylacetamide, dimethyl sulfonamide, and N,N-dimethylformamide as good solvents for a gallium phthalocyanine.
However, there is room for improvement in the solubility of gallium phthalocyanine in N-methylpyrrolidone, dimethyl sulfoxide, dimethylacetamide, dimethyl sulfonamide, or N,N-dimethylformamide.